Previous studies have shown that intraocular pressure (IOP) plays an essential role in coordinating the growth of all ocular tissues in the mbryo. The goal of this project is to examine the tissue interactions which control the development of the ciliary body and to determine whether the ciliary epithelium generated IOP in the embryo, as it does in adults. This will be accomplished by three approaches: 1) a morphological and biochemical analysis of the development of the ciliary body 2) an experimental analysis of the inductive interactions responsible for the formation of the ciliary epithelium and ciliary muscle, and 3) a physiological study of the time of onset of fluid transport by the ciliary epithelium. The techniques to be used include electron microscopy, in vivo microsurgery, in ovo and in vitro measurement of IOP, histochemistry, immunocytochemistry, gel electrophoresis, light microscopic histology, electrophysiology, and pharmacologic treatment of the eye and isolated ocular tissues. The results of these studies are expected to provide important information on the origins of the tissues of the ciliary body and their role in normal and abnormal ocular development. It is likely that this work, because of some unique advantages in studying embryonic tissues, will give greater insight into the function of the adult ciliary epithelium.